1. Field of the Invention
This invention relates to an automatic transmission control system for controlling an automatic transmission for use in a vehicle provided with a throttle control means which electrically controls a throttle valve to control the engine output according to the amount of depression of the accelerator pedal of the vehicle and a constant-speed cruising control system which makes the vehicle cruise at a desired constant speed.
2. Description of the Prior Art
There has been known a vehicle provided with a throttle control means which electrically controls the throttle valve according to the amount of depression of the accelerator pedal, a constant-speed cruising control system which controls the throttle valve independently from the operation of the accelerator pedal to keep the actual vehicle speed constant at a desired constant speed, and an automatic transmission which is controlled with a predetermined gear-shifting pattern according to the amount of depression of the accelerator pedal and the vehicle speed. For example, see Japanese unexamined patent publication No. 57(1982)-196317.
The throttle valve is controlled to open the throttle according to the amount of depression of the accelerator pedal when the constant-speed cruising control is not performed, while when the constant-speed cruising control is performed, the throttle valve is controlled to converge on a target throttle opening obtained on the basis of the difference between the actual vehicle speed and the target vehicle speed (desired vehicle speed), thereby feedback-controlling the engine output to keep the vehicle speed constant at the target vehicle speed without operation of the accelerator pedal.
In the case of an automatic transmission for a vehicle provided with such a throttle control means and a constant-speed cruising control system, gear-shifting is controlled according to the amount of depression of the accelerator pedal and the vehicle speed. However, while the constant-speed cruising control is performed, the accelerator pedal is not operated, and accordingly, the amount of depression does not represent the driver's engine output requirement. Therefore, the gear-shifting cannot be controlled on the basis of the detected amount of depression of the accelerator pedal.
That is, during the time when the constant-speed cruising control is performed, the acceleration pedal is operatively separated from the throttle valve, and even if the throttle valve is open, there is no depression of the accelerator pedal.
On the other hand, when the throttle valve is controlled in response to operation of the accelerator pedal, the change in the throttle opening does not strictly follow the change in the amount of depression of the accelerator pedal. Instead the change in the amount of depression of the accelerator pedal is transmitted to the throttle after various corrections such as delaying. Accordingly, when the engine output is controlled in response to the operation of the accelerator pedal by the driver, it is preferable that gear-shifting be controlled according to the amount of depression of the accelerator pedal in order to meet driver's requirements, e.g., a quick response to kickdown.